Heading east on the Great Plains yesterday afternoon, we encountered a dense cloud bank that stretched across the eastern horizon. It had the appearance of a massive mountain ridge, topped by a pink layer of snow that reflected the setting sun.
As we continued eastward beneath a clear sky and enveloped in mild air, the dark ridge of clouds rose higher. Finally, when we stopped for the night in Colby, Kansas, the atmospheric wall loomed above the city, evoking the image of a towering mesa in the twilight of dusk.
In fact, the wall was the western edge of an Arctic trough that is plunging through the Heartland. While the temperature in Colby was in the low 30s (F), the air east of the "ridge" was in the teens. Though one often encounters cloud formations along the edge of fronts, this Arctic wall was especially striking in appearance, reflecting a dramatic clash of air masses; today, we'll pierce that barrier and enter the depths of winter.